Shared Core

Description

The Shared Core (S-CORE) is a fundamental architectural principle defined within 3GPP for enabling network sharing. It allows multiple participating operators or tenants to utilize a single, common core network (CN) infrastructure, which includes network functions like the AMF, SMF, UPF, and UDM. The architecture is designed to ensure logical isolation between the sharing partners, meaning each operator's subscribers, policies, and data are kept separate and secure. This is achieved through the use of dedicated identifiers, such as specific PLMN IDs, and network slice instances that are logically partitioned within the shared physical resources.

From an operational perspective, S-CORE introduces specific management and orchestration capabilities. The shared infrastructure is managed by a hosting party, which could be one of the participating operators or a neutral host. Each sharing operator retains control over its own subscriber management, policy control, and service provisioning. The 3GPP specifications define reference points and procedures to support this split responsibility, ensuring that an operator can independently authenticate its users, apply its own QoS policies, and manage charging records without interference from other operators sharing the core.

The implementation of S-CORE is crucial for several deployment scenarios. It is the foundation for Mobile Virtual Network Operator (MVNO) arrangements, where an MVNO does not own radio access network (RAN) infrastructure but relies on a host MNO's core. It is also essential for national roaming agreements and, more recently, for enabling efficient network slicing in 5G. In a network slicing context, different slices (e.g., for enhanced Mobile Broadband, Massive IoT, or Ultra-Reliable Low-Latency Communications) can be instantiated on a shared S-CORE platform, with each slice representing a logically isolated network serving a specific tenant or service type. The specifications, particularly TS 32.130 and TS 32.851, detail the management and orchestration aspects, including service-level agreement (SLA) fulfillment, fault management segregation, and performance reporting per sharing entity.

Purpose & Motivation

S-CORE was introduced to address the high capital expenditure (CAPEX) and operational expenditure (OPEX) associated with deploying and maintaining independent core networks, especially for new market entrants or in scenarios with low initial subscriber density. Prior to standardized network sharing, operators had to build entirely separate core networks, leading to inefficient resource utilization and higher costs. S-CORE provides a standardized framework that enables infrastructure sharing while preserving each operator's brand identity, service differentiation, and control over their subscribers.

The motivation stems from both economic and regulatory drivers. Economically, it lowers the barrier to entry for new operators and allows existing operators to monetize excess capacity. Regulators in many regions promote network sharing to accelerate coverage rollout, particularly in rural areas, and to reduce environmental impact by minimizing duplicate infrastructure. The concept evolved to support more dynamic and flexible sharing models required for 5G, where network slicing demands a core network that can be partitioned on-demand for diverse vertical industries. S-CORE solves the problem of rigid, physically separate cores by providing a scalable, multi-tenant architecture that maintains the necessary security and operational independence.